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Subject[PATCH v2] dmaengine: sprd: Support DMA link-list mode
Date
From: Eric Long <eric.long@spreadtrum.com>

The Spreadtrum DMA can support the link-list transaction mode, which means
DMA controller can do transaction one by one automatically once we linked
these transaction by link-list register.

Signed-off-by: Eric Long <eric.long@spreadtrum.com>
Signed-off-by: Baolin Wang <baolin.wang@linaro.org>
---
Changes since v1:
- Remove sprd_dma_fill_chn_desc() function.
- Remove the redundant validation of 'sglen' in sprd_dma_fill_linklist_desc().
- Add some comments make code more clear.
- Fix the typos.
---
drivers/dma/sprd-dma.c | 81 ++++++++++++++++++++++++++++++++++++++----
include/linux/dma/sprd-dma.h | 69 +++++++++++++++++++++++++++++++++++
2 files changed, 143 insertions(+), 7 deletions(-)

diff --git a/drivers/dma/sprd-dma.c b/drivers/dma/sprd-dma.c
index 55df0d4..38d4e4f 100644
--- a/drivers/dma/sprd-dma.c
+++ b/drivers/dma/sprd-dma.c
@@ -68,6 +68,7 @@

/* SPRD_DMA_CHN_CFG register definition */
#define SPRD_DMA_CHN_EN BIT(0)
+#define SPRD_DMA_LINKLIST_EN BIT(4)
#define SPRD_DMA_WAIT_BDONE_OFFSET 24
#define SPRD_DMA_DONOT_WAIT_BDONE 1

@@ -103,7 +104,7 @@
#define SPRD_DMA_REQ_MODE_MASK GENMASK(1, 0)
#define SPRD_DMA_FIX_SEL_OFFSET 21
#define SPRD_DMA_FIX_EN_OFFSET 20
-#define SPRD_DMA_LLIST_END_OFFSET 19
+#define SPRD_DMA_LLIST_END BIT(19)
#define SPRD_DMA_FRG_LEN_MASK GENMASK(16, 0)

/* SPRD_DMA_CHN_BLK_LEN register definition */
@@ -164,6 +165,7 @@ struct sprd_dma_desc {
struct sprd_dma_chn {
struct virt_dma_chan vc;
void __iomem *chn_base;
+ struct sprd_dma_linklist linklist;
struct dma_slave_config slave_cfg;
u32 chn_num;
u32 dev_id;
@@ -582,7 +584,8 @@ static int sprd_dma_get_step(enum dma_slave_buswidth buswidth)
}

static int sprd_dma_fill_desc(struct dma_chan *chan,
- struct sprd_dma_desc *sdesc,
+ struct sprd_dma_chn_hw *hw,
+ unsigned int sglen, int sg_index,
dma_addr_t src, dma_addr_t dst, u32 len,
enum dma_transfer_direction dir,
unsigned long flags,
@@ -590,7 +593,6 @@ static int sprd_dma_fill_desc(struct dma_chan *chan,
{
struct sprd_dma_dev *sdev = to_sprd_dma_dev(chan);
struct sprd_dma_chn *schan = to_sprd_dma_chan(chan);
- struct sprd_dma_chn_hw *hw = &sdesc->chn_hw;
u32 req_mode = (flags >> SPRD_DMA_REQ_SHIFT) & SPRD_DMA_REQ_MODE_MASK;
u32 int_mode = flags & SPRD_DMA_INT_MASK;
int src_datawidth, dst_datawidth, src_step, dst_step;
@@ -670,12 +672,52 @@ static int sprd_dma_fill_desc(struct dma_chan *chan,
temp |= (src_step & SPRD_DMA_TRSF_STEP_MASK) << SPRD_DMA_SRC_TRSF_STEP_OFFSET;
hw->trsf_step = temp;

+ /* link-list configuration */
+ if (schan->linklist.phy_addr) {
+ if (sg_index == sglen - 1)
+ hw->frg_len |= SPRD_DMA_LLIST_END;
+
+ hw->cfg |= SPRD_DMA_LINKLIST_EN;
+
+ /* link-list index */
+ temp = (sg_index + 1) % sglen;
+ /* Next link-list configuration's physical address offset */
+ temp = temp * sizeof(*hw) + SPRD_DMA_CHN_SRC_ADDR;
+ /*
+ * Set the link-list pointer point to next link-list
+ * configuration's physical address.
+ */
+ hw->llist_ptr = schan->linklist.phy_addr + temp;
+ } else {
+ hw->llist_ptr = 0;
+ }
+
hw->frg_step = 0;
hw->src_blk_step = 0;
hw->des_blk_step = 0;
return 0;
}

+static int sprd_dma_fill_linklist_desc(struct dma_chan *chan,
+ unsigned int sglen, int sg_index,
+ dma_addr_t src, dma_addr_t dst, u32 len,
+ enum dma_transfer_direction dir,
+ unsigned long flags,
+ struct dma_slave_config *slave_cfg)
+{
+ struct sprd_dma_chn *schan = to_sprd_dma_chan(chan);
+ struct sprd_dma_chn_hw *hw;
+
+ if (!schan->linklist.virt_addr)
+ return -EINVAL;
+
+ hw = (struct sprd_dma_chn_hw *)(schan->linklist.virt_addr +
+ sg_index * sizeof(*hw));
+
+ return sprd_dma_fill_desc(chan, hw, sglen, sg_index, src, dst, len,
+ dir, flags, slave_cfg);
+}
+
static struct dma_async_tx_descriptor *
sprd_dma_prep_dma_memcpy(struct dma_chan *chan, dma_addr_t dest, dma_addr_t src,
size_t len, unsigned long flags)
@@ -744,10 +786,20 @@ static int sprd_dma_fill_desc(struct dma_chan *chan,
u32 len = 0;
int ret, i;

- /* TODO: now we only support one sg for each DMA configuration. */
- if (!is_slave_direction(dir) || sglen > 1)
+ if (!is_slave_direction(dir))
return NULL;

+ if (context) {
+ struct sprd_dma_linklist *ll_cfg =
+ (struct sprd_dma_linklist *)context;
+
+ schan->linklist.phy_addr = ll_cfg->phy_addr;
+ schan->linklist.virt_addr = ll_cfg->virt_addr;
+ } else {
+ schan->linklist.phy_addr = 0;
+ schan->linklist.virt_addr = 0;
+ }
+
sdesc = kzalloc(sizeof(*sdesc), GFP_NOWAIT);
if (!sdesc)
return NULL;
@@ -762,10 +814,25 @@ static int sprd_dma_fill_desc(struct dma_chan *chan,
src = slave_cfg->src_addr;
dst = sg_dma_address(sg);
}
+
+ /*
+ * The link-list mode needs at least 2 link-list
+ * configurations. If there is only one sg, it doesn't
+ * need to fill the link-list configuration.
+ */
+ if (sglen < 2)
+ break;
+
+ ret = sprd_dma_fill_linklist_desc(chan, sglen, i, src, dst, len,
+ dir, flags, slave_cfg);
+ if (ret) {
+ kfree(sdesc);
+ return NULL;
+ }
}

- ret = sprd_dma_fill_desc(chan, sdesc, src, dst, len, dir, flags,
- slave_cfg);
+ ret = sprd_dma_fill_desc(chan, &sdesc->chn_hw, 0, 0, src, dst, len,
+ dir, flags, slave_cfg);
if (ret) {
kfree(sdesc);
return NULL;
diff --git a/include/linux/dma/sprd-dma.h b/include/linux/dma/sprd-dma.h
index b0115e3..b42b80e5 100644
--- a/include/linux/dma/sprd-dma.h
+++ b/include/linux/dma/sprd-dma.h
@@ -58,4 +58,73 @@ enum sprd_dma_int_type {
SPRD_DMA_CFGERR_INT,
};

+/*
+ * struct sprd_dma_linklist - DMA link-list address structure
+ * @virt_addr: link-list virtual address to configure link-list node
+ * @phy_addr: link-list physical address to link DMA transfer
+ *
+ * The Spreadtrum DMA controller supports the link-list mode, that means slaves
+ * can supply several groups configurations (each configuration represents one
+ * DMA transfer) saved in memory, and DMA controller will link these groups
+ * configurations by writing the physical address of each configuration into the
+ * link-list register.
+ *
+ * Just as shown below, the link-list pointer register will be pointed to the
+ * physical address of 'configuration 1', and the 'configuration 1' link-list
+ * pointer will be pointed to 'configuration 2', and so on.
+ * Once trigger the DMA transfer, the DMA controller will load 'configuration
+ * 1' to its registers automatically, after 'configuration 1' transaction is
+ * done, DMA controller will load 'configuration 2' automatically, until all
+ * DMA transactions are done.
+ *
+ * Note: The last link-list pointer should point to the physical address
+ * of 'configuration 1', which can avoid DMA controller loads incorrect
+ * configuration when the last configuration transaction is done.
+ *
+ * DMA controller linklist memory
+ * ====================== -----------------------
+ *| | | configuration 1 |<---
+ *| DMA controller | ------->| | |
+ *| | | | | |
+ *| | | | | |
+ *| | | | | |
+ *| linklist pointer reg |---- ----| linklist pointer | |
+ * ====================== | ----------------------- |
+ * | |
+ * | ----------------------- |
+ * | | configuration 2 | |
+ * --->| | |
+ * | | |
+ * | | |
+ * | | |
+ * ----| linklist pointer | |
+ * | ----------------------- |
+ * | |
+ * | ----------------------- |
+ * | | configuration 3 | |
+ * --->| | |
+ * | | |
+ * | . | |
+ * . |
+ * . |
+ * . |
+ * | . |
+ * | ----------------------- |
+ * | | configuration n | |
+ * --->| | |
+ * | | |
+ * | | |
+ * | | |
+ * | linklist pointer |----
+ * -----------------------
+ *
+ * To support the link-list mode, DMA slaves should allocate one segment memory
+ * from always-on IRAM or dma coherent memory to store these groups of DMA
+ * configuration, and pass the virtual and physical address to DMA controller.
+ */
+struct sprd_dma_linklist {
+ unsigned long virt_addr;
+ phys_addr_t phy_addr;
+};
+
#endif
--
1.7.9.5
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